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An international team led by the University of Cambridge set out the CosmoCube mission in a paper published in Nature Astronomy on 14 August 2026.
CosmoCube is a proposed suitcase-sized satellite that would orbit the Moon and listen for the 21-centimetre hydrogen signal from the cosmic Dark Ages, more than 13.5 billion years ago.
It would use the Moon's far side as a natural shield against radio interference from Earth, getting about 40 minutes of quiet observing in every two-hour orbit.
Over a proposed two-year mission it could gather roughly 1,000 hours of data at very low radio frequencies, in the region of 10-50 MHz.
India has its own version of the idea: PRATUSH, a lunar-orbit radiometer proposed by the Raman Research Institute with ISRO, and the ground-based SARAS series that refuted the 2018 EDGES claim.
After the Big Bang and the release of the cosmic microwave background, the universe went dark. There were no stars and no galaxies, only a cold fog of neutral hydrogen, for roughly 150 million years. That period is called the cosmic Dark Ages, and it ended with Cosmic Dawn, when the first stars ignited. Nothing in that era emitted visible light, so the only messenger available is the 21-centimetre line, a faint radio emission produced when the spin of a hydrogen atom's electron flips relative to its proton. Because the universe has expanded since, that signal reaches us stretched to much longer wavelengths - which is why CosmoCube must observe at very low radio frequencies of about 10-50 MHz, exactly the band that Earth's own transmitters and ionosphere ruin.
Simple Analogy: It is like trying to hear a whisper from the next room while a loud concert plays beside you. The only fix is to walk behind a thick wall - and the far side of the Moon is the thickest radio wall available anywhere near Earth.
India's counterpart concept - a lunar-orbit radiometer developed by the Raman Research Institute, Bengaluru, with ISRO, proposed in a 2018 announcement of opportunity and still in pre-project studies. It would carry a wideband frequency-independent antenna over 30-250 MHz, optimised for the Cosmic Dawn band of 55-110 MHz, with a first phase in low Earth orbit.
A US experiment reported in Nature that it had detected the absorption signature of Cosmic Dawn, a result that would have been the first direct evidence of the first stars.
The Raman Research Institute's indigenously built ground-based radiometer, deployed on lakes, measured the 55-85 MHz sky spectrum and reported in Nature Astronomy that the EDGES profile was not of astrophysical origin, rejecting the best-fit profile with 95.3% confidence. It was the first telescope anywhere to reach the sensitivity needed to test the claim.
It is permanently turned away from Earth, so the Moon's bulk shields an instrument there from terrestrial radio transmissions and from the ionospheric distortion that limits ground-based 21-cm experiments.
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What specific physical quantity ensures a satellite maintains its orbit without continuous propulsion?
Answer: Orbital velocity
Radio emission from neutral hydrogen produced by a spin-flip transition of its electron; the only signal available from the cosmic Dark Ages.
The roughly 150-million-year period after the cosmic microwave background was released and before the first stars formed, when the universe held no luminous sources.
The epoch in which the first stars and galaxies ignited, ending the Dark Ages.
An instrument that measures the total power of radio emission across a frequency band, as opposed to imaging individual sources.
The stretching of a wave to longer wavelengths as the universe expands, which is why a 21-centimetre signal arrives as a metres-long radio wave.